The present invention relates to a method and a drive train for performing a gearshift in a vehicle provided with a manual transmission or an automated manual transmission. A drivetrain incorporating said transmission comprises an engine, connected via a clutch to the transmission. An electric motor/generator is drivingly connected to said drivetrain and arranged between said clutch and said transmission or between said combustion engine and said clutch. The electric motor/generator is connected to an energy storing means and/or an energy consumer.
Automated manual transmissions for various kinds of vehicles are well known by persons skilled in the art. Such transmissions arc more or less identical to manual transmissions, but clutch operation and gear shift operation have been automated.
One problem, common for both manual and automated manual transmissions, is that the power transfer from engine to drive wheels is interrupted during a gear change. Except for the loss of torque during the gear change, the power transmission interrupt is problematic especially for turbo-charged engines, since the turbo pressure is lost during the power interrupt. The loss of turbo-pressure is detrimental to emissions and fuel economy, and also prolongs the period during which the driver is unable to control the engine to supply the driving wheels with sufficient driving torque.
In the known prior art, similar problems have been addressed in several patent documents. For example, U.S. Pat. No. 6,022,290 relates to a power transfer system reducing the torque loss experienced during a gear shift. The system includes an epicyclic gearset for providing a drive torque to the drive wheels during a gear shift of the automated manual transmission. The system is aimed towards providing the drive wheels with a torque during gear shift operations of the automated manual transmission via a parallel propulsion force way to the wheels. U.S. Pat. No. 6,022,290 also relates to an electronic throttle control reducing engine power output during the gearshifts.
U.S. Pat. No. 6,135,913 is a divisional application stemming from U.S. Pat. No. 6,022,290; its scope of protection includes that some kind of energy reservoir should be used for providing the driving wheels with torque during gearshift operations.
EP 1 669 638 relates to a transmission system comprising a first and a second transmission. An electromagnetic brake, the purpose of which is to engage the second transmission during a gearshift of the first transmission, is provided to engage and disengage the second transmission.
Lastly, US 2002/0065168 relates to a transmission connected to a first prime mover (an engine) and a second prime mover (an electric motor). The engine and the motor are arranged such that the motor provides the transmission with a drive torque during gearshifts.
Although some of the above mentioned arrangements in said patent documents might solve the problem with loss of turbo pressure during a gear shift, the proposed solutions are all very complicated; rather than addressing the problem with loss of turbo pressure, they address the problem with loss of drive torque during the gear shift.
One purpose of the present invention is to provide a method for at least avoiding an unloaded super charger during a gearshift of an automated manual transmission.
An aspect of the invention solves this problem by providing a method comprising the steps of controlling the motor/generator to provide a torque equalling or at least equalling the torque provided by the combustion engine, such that the manual transmission or the automated manual transmission transfers an only minor, or no, torque, disengaging presently engaged gear with a first gear ratio, controlling the torques provided by the motor/generator and the engine such that a rotational speed of said combustion engine correlates or almost correlates to a rotational speed necessary for propelling the vehicle at a selected new gear with a second gear ratio, and engaging said new selected gear.
In order to use the energy provided by the motor/generator during the gearshift, the electrical energy produced by the motor/generator could be transferred to an energy storage means and/or an energy consumer.
The energy storage means can be a battery or a capacitor. If for example the battery should be fully loaded, the electrical energy produced by the motor/generator could be transferred to an energy consumer, such as a heating element.
In order to reduce risk of overheating the heating element, the heating element could be cooled by the vehicle's cooling system.
Three of the major benefits of aspects of the present invention are;
the ability to avoid a super charger of said combustion engine being unloaded during said gearshift, when said clutch is disengaged,
or to adapt a turbo pressure of a super charger of said combustion engine during the gearshift to said new selected gear that will be engaged,
or to maintain a turbo pressure of a super charger of said combustion engine during the gearshift, when said clutch is disengaged.
In a further aspect of the invention injection timing or ignition timing of fuel injected in the combustion engine during the gearshift will increase the turbo pressure for a specific engine load.